This renewal application of our Program Project consists of four projects employing lipid bilayers, membrane vessicles and patches, perfused papillary muscles and intact in situ hearts which explore the causes of the electrical abnormalities underlying ischemia-induced ventricular fibrillation and sudden cardiac death. The projects are supported by an Animal/Laboratory Support core (A), a Technical Core (B), and an Administrative Core (C) and are also united by their use of common preparations and common technologies. The in situ pig heart with a carotid to left anterior descending (LAD) coronary artery shunt is used in Projects 1 to explore a unique model of reproducible ventricular fibrillation which occurs when the interruption of flow through the LAD shunt is preceded by the elevation of potassium in the LAD distribution. The project seeks to characterize and to determine the causes of the very slow conduction which invariably precedes ventricular fibrillation. It will also employ the intact perfused rabbit papillary muscle preparation used in Project 2 to test the hypothesis that CO2 diffusion at the border between ischemic and nonischemic tissues causes inhomogeneous changes in intracellular pH and calcium that result in inhomogeneous electrical changes, including very slow conduction. Project 3 uses lipid bilayers to determine the effects of changes in intracellular pH, calcium and magnesium on the voltage dependent L-type calcium channel in order to better understand the factors causing the rise in intracellular calcium that is thought to underlie many of the ischemia induced electrical events. The Technical Core provides electrode, electronic, and computer support. It takes advantage of unique interactions within and without the University of North Carolina to develop new capabilities which will be directly applied to the individual projects. Our program reflects a maturation of our concepts over the last five years and involves investigators from the Departments of Medicine, Biochemistry and Biophysics, Cell Biology and Anatomy, Pharmacology, Biomedical Engineering, and Biostatistics and includes extensive interaction and collaboration with investigators at Duke University, North Carolina State University, and the National Institutes for Environment Health Sciences, The Department of Experimental Cardiology at the University of Amsterdam, the Netherlands, and the Physiologisches Institut, University of Bern, Switzerland.